| Specific gravity | 1014· |
| Water | 966·10 |
| Solid constituents | 33·90 |
| Urea | 4·77 |
| Uric acid | 0·40 |
| Fixed salts | 8·04 |
| Extractive matters | 2·40 |
| Albumen | 18·00 |
No. 2 (Dr Percy).
| Specific gravity | 1020· |
| Water | 946·82 |
| Solid constituents | 53·18 |
| Urea | 7·68 |
| Uric acid, and indeterminate animal matter | 17·52 |
| Fixed soluble salts | 5·20 |
| Earthy phosphates | 0·14 |
| Albumen | 22·64 |
Dr Parkes records the case of a patient suffering from albuminuria, who excreted 545 grains of albumen in twenty-four hours. See Urates.
Urine frequently contains an abnormally large quantity of urea. Such urine is of high specific gravity—1·030 or more. When present in large excess the urea becomes deposited in ‘sparkling crystalline lamellæ’ of the nitrate, if it be mixed with an equal quantity of strong nitric acid in the cold.
The crystals vary slightly in character, according to the amount of nitric acid employed and the degree of concentration of the urine. Urine which thus yields, without previous concentration, the nitrate, is said to contain an excess of urea. See page 1689.
The quantity of urea present in urine is best determined by a process invented by Liebig. When a solution of pernitrate of mercury is added to one of pure urea the urea and mercuric salt unite and form an insoluble compound, of undetermined constitution. If, however, the chlorides of the alkalies and alkaline earths are present, this combination does not take place, owing to the decomposition of the mercuric nitrate, and the formation of bichloride of mercury, and a nitrate of the alkali or alkaline earth, both of which are soluble. When, however, the decomposition of the chloride has been completed, the urea may be entirely precipitated, provided a sufficient quantity of mercuric nitrate be added to the solution. In estimating the amount of urea in urine, therefore, it is only necessary to add to the urine a solution of the mercuric salt of known strength, since from the quantity of this latter which has been employed in throwing down the urea, this can easily be calculated.
In performing this analysis, three special solutions are requisite:
1. A solution consisting of one part by measure of a cold saturated solution of barium nitrate with two parts (also by measure) of saturated baryta water. This serves for the removal of the phosphates and sulphates, the presence of which in the urine would interfere with the analysis.
2. The standard solution of mercuric nitrate, which is made as follows:—772 grains of red oxide of mercury placed in a beaker are dissolved in a sufficient quantity of nitric acid (sp. gr. 1·20) by a gentle heat, and evaporated